4. To assemble the coulibiac, roll one of the blocks of puff pastry out to a rectangle 4cm/1½in bigger all round than the salmon fillets. Roll out the second block to make a rectangle 5cm/2in
larger than the first one. (You may not need to use all the pastry.) Sprinkle half of the spinach leaves over the smaller sheet of puff pastry, leaving a 2cm/¾in gap around the edge of the pastry.
Place one of the salmon fillets on top of the spinach leaves, then spread the filling mixture over the salmon. Place the second salmon fillet on top of the filling mixture to make a ‘sandwich’.
Cover the salmon with the remaining spinach leaves.

5. Brush the edges of the puff pastry with beaten egg and cover the salmon filling with the second, larger, sheet of puff pastry. Seal the edges of the pastry parcel together with your fingers,
trimming off any excess. Carefully transfer the salmon coulibiac to a greased baking tray.

6. Using a knife, cut one or two small holes in the top of the salmon coulibiac, then brush all over with the remaining beaten egg. Transfer the salmon coulibiac to the oven and bake for 25-30
minutes, or until the pastry is crisp and golden-brown.